Character display panel having a plurality of glow discharge cavities including resistive ballast means exposed to the glow discharge therein



g- 1957 RC. LHEUREUX 3,334,269 ITY OF GLOW E BALLAS THE GLOW DISCHARGE THEREIN CHARACTER DISPLAY PANEL HAVING A PLURAL DISCHARGE CAVITIES INCLUDING RESISIIV MEANS EXPOSED TO Filed July 28, 1964 5 Sheets-Sheet l R W W W.

4 \M E l v 1 .0 M. Z 0 Z 5 d, H .7 Z V 2 M w Aug. 1, 1967 R. c. LHEUREUX 3,334,269

CHARACTER DISPLAY PANEL HAVING A PLURALITY OF GLOW DISCHARGE CAVITIES INCLUDING RESISTIVE BALLAST MEANS EXPOSED TO THE GLOW DISCHARGE THEREIN Filed July 28, 1964 3 Sheets-Sheet 2 I N VE N TOR. 26621 C. L Wearaax BY WWQ M g- 19167 R. c. LHEUREUX 3,334,269

CHARACTER DISPLAY PANEL HAVING A PLURALIITY OF GLOW DISCHARGE CAVITIES INCLUDING RESISTIVE BALLAST MEANS EXPOSED TO THE GLOW DISCHARGE THEREIN 1964 3 Sheets-Sheet 3 Filed July 28,

i l E U} INVENTOR.

M w wm a a M. Z 4 w i United States Patent This invention relates generally to devices for selectively forming and displaying a plurality of characters, such as letters and numerals, and more particularly to a character display panel employing an array of fluorescent lamp elements.

In the computer and instrumentation technologies, it is frequently desirable to provide a read-out device for visually displaying different characters; in airborne ap- 3,334,269 Patented Aug. 1, 1967 FIG. 6 is a fragmentary end view illustrating a still further embodiment of the invention; and

FIG. 7 is a cross-sectional view taken along line 7-7 of FIG. 6. I

Referring now to FIGS. 1 and 2, there is shown a min iature character display panel, generally indicated at 10, comprising a flat cathode plate 11 in order to provide support for the other elements of the device and to impart the requisite rigidity. Cathode plate 11 is preferably formed of suitable metal having good thermal conductivity, such as aluminum, in order to conduct away heat generated in the individual fluorescent lamp elements due to the arc discharge therein, as will be hereinafter more fully described. Cathode plate 11 may also be plications in which size and weight factors are critical,

it is desirable that such read-out devices be highly miniaturized. A common form of character display device employs a plurality of individual incandescent lamps arranged in a predetermined pattern or array so that selective illumination of the lamps forms and displays the desired characters. While miniature incandescent lamps are commercially available, employment of a large number of such lamps in an array nevertheless provides a device of objectionable size. Furthermore, employment of a large number of incandescent lamps in an array necessitates accommodation of a large number of electrical leads extending from the lamps and provision must be made for disassembling the device in order to replace burned-out lamps. In addition, any device employing incandescent lamps inherently is subject to damage due to shock.

It is therefore desirable to provide a character display panel which lends itself to miniaturization and which does not employ incandescent lamps for the light sources.

It is accordingly an object of the invention to provide an improved character display panel,

Another object of the invention is to provide an improved character display panel capable of being highly miniaturized.

The invention in its broader aspects provides a character display panel comprising a self-contained array of in,- dividual fluorescent lamp elements. Each of these elements may have a very small internal diameter and-the elements may be closely packed in a planar array for viewing from their ends thus permitting the provision of an extremely miniaturized device in which the electrical connections are simplified and importantly in which filaments are eliminated thus eliminating the necessity for disassembling the device for lamp replacement.

The above-mentioned and other features and objects of this invention and the manner of attaining them will become more apparent and the invention itself will bebest understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a fragmentary cross-sectional view of one embodiment of the invention;

FIG. 2 is a fragmentary exploded view, partly in crosssection and partly broken'away, further illustrating the embodiment of FIG. 1

FIG. 3 is a fragmentary cross-sectional ing another embodiment of the invention;

FIG. 4 is a fragmentary cross-sectional view illustrating yet another embodiment of the invention;

FIG. 5 is a fragmentary view in perspective illustrating a modification of the embodiment of FIG. 1;

view illustratformed of electrical insulation material having good thermal conductive properties, such as beryllium oxide or aluminum oxide. In the case of a cathode plate 11 formed of electrically conductive material, a thin layer 12 of insulating material is deposited or otherwise formed on the inner surface 13, as by anodizing in the case of aluminum. A plurality of elongated, spaced, parallel conductive strips 14 are formed or adhered to the surface of the insulating layer 12, as shown.

A layer 15 of suitable resistive material is deposited over the insulating layer 12 and the conductive strips 14. Resistive layer 15 serves to limit or ballast the glow discharge cnrrent, as will be hereinafter more fully described.

- 17 and surface 20.

A member 16 is provided having fiat opposite sides 17, 18 and with its side 17 abutting the resistive layer 15, as shown. A recess 19 is formed in side 18 of member 16 and has a flat bottom surface 20 parallel with the side 17. A plurality of closely spaced cylindrical cavities or openings 22 are formed in member 16 extending transversely between sides 17 and surface 20; in the preferred embodiment shown, the axes of openings 22 are parallel and respectively perpendicular to the planes of sides Each of the openings 22 has its end 23' which communicates with side'17 of member 16 in registry with a conductive strip 14. In the preferred embodiment of the invention, areas 24 of material, such as nickel, nichrome, etc. having secondary electron emission characteristics are deposited on the surface on the resistive layer 15 and are respectively disposed to the ends 23 of the openings 22.

Another flat plate member 25 is provided formed of light-transmitting material, such as glass. A plurality of elongated, spa parallel, conductive strips 26, also having light-transmitting characteristics, are secured or deposited on the inner surface 27 of plate 25. As best seen in FIG. 2, the conductive strips 26, which are preferably formed of transparent conductive material, extend transversely with respect to the conductive strips 14, and each of the openings 22 in member 16 has its other end 27 in registry with a conductive strip 26. p

In the embodiment of FIGS. 1 and 2, a layer 28 of suitable phosphor material, such as Sylvania #5702 which emits visible light when stimulated by ultra-violet light, is deposited over the inner surface 31 of plate 25 and over the conductive strips 26. Plate member 25 with conductive strips 26 and phosphor layer 28 thereon is arranged with the phosphor layer 28 abutting side 18,0f member 16, the phosphor layer 28 thus being exposed to) cavity 19 and ends 27 of the openings 22.

The openings or cells 22 and the channel formed by recess 19 which, it will be seen, interconnects ends 27 of the openings 22, is filled with the proper mixture of mercury and argon gas at the proper pressure to provide a glow discharge having the desired spectral characteristic at the operating voltage employed; in the preferred embodiment, the mercury-argon mixture and pressure is selected to generate ultra-violet light of 2537 A. at an operating or holding voltage of the order of 260 volts. The gas pressures employed are similar to those employed in conventional fluorescent lamps adjusted in accordance with the geometry of the openings 22 and the operating voltages employed, is well known to those skilled in the art. The channel defined by the recess 19 which interconnects the cells or openings 22 equalizes the pressure-s and gas mixtures in each of the cells.

The openings 22 and channel 19 are initially filled with gas by means of passageway 29 communicating with channel 19, passageway 29 being sealed as at 30 when the proper pressure has been obtained. The elements forming the panel are held in assembled relation and sealed by means of a clamping element 32, as shown.

It will now be seen that each of the cells or openings 22 is filled with gas, has one conductive strip 14 at its one end 23 and another conductive strip 26 at its other end 27, and has the phosphor material 28 exposed to its end 27. Each of the cells or openings 22 thus forms an individual fluorescent lamp. Thus, upon application of a suitable breakdown or sparking potential to the two conductive strips 14, 26 with which the two ends 23, 27 of one cell 22 are in registry, break-down of the gas in which the two conductive strips or electrodes are immersed occurs and a self-sustained arc discharge will be initiated between the two conductive strips 14, 26. It is well known that such an arc discharge has a negative resistance characteristic, i.e., as the current increases the resistance decreases. Thus, unless the voltage which was required initially to produce the discharge is rapidly -reduced to a lower level, the current will very rapidly increase to a destructive level. This reduction in operating voltage may be provided by the current-limiting resistance layer 12 and/ or the immediate application of a lower operating or holding potential across the two eflective conductive strips 14, 26. It will further be seen that so long as the operating or holding potential is maintained across the two effective conductive strips 14, 26 the arc discharge in the respective cell 22 will be maintained; removal of the holding potential or pulsing of the applied voltage to a lower level will extinguish the are. As indicated, the are or glow discharge generates ultra-violet light which in turn activates or stimulates the phosphor layer 28 exposed to the respective cell 22 causing it to emit visible light, in the same manner as a conventional fluorescent lamp.

It will now be seen that the transversely disposed conductive strips 14, 26 form a matrix arrangement with the result that selective application of a potential across one of the strips 14 and one of the strips 26 will cause illumination of the respective cell 22. In this manner, different characters, such as letters or numerals, may be formed and displayed by selective application of potential to predetermined strips 14, 26 thus illuminating predetermined ones of the cells 22.

Referring particularly to FIG. 2, one possible switching arrangement is shown, it being understood that the switching arrangement by which potentials are applied to the respective conductive strips 14, 26 does not form a part of the invention and is shown for illustrative purposes only. Here, each of the conductive strips 14 is coupled to a switch 33 having first and second positions 34 and 35, the position 34 being coupled to source 36 of holding potential, such as 260 volts, and position 35 being coupled to another source of potential 37. The other conductive strips 26 are coupled to switches 38 respectively having first and second positions 39, 40. Switch positions 39 are coupled to switch 42 having a first and second position 43, 44. Switch position 43 is coupled to the other side of potential sources 36, 37 while switch position 44 is coupled to source 45 which reduces the holding potential source 36 to a lower arc extinguishing level. Switch positions 40 are coupled to potential source 46 which, together with source 37, provides a higher sparking or breakdown potential for initiating the arc discharge. In operation, if it is desired to illuminate cell 22a, the switches 33a and 38a are momentarily and simultaneously moved to their positions 35, 40 thus applying the sum of the potentials of sources 37, 46 across conductive strips 14a, 26a, and thereby to initiate the arc discharge in the cell 22a. Switches 33a, 380 are then immediately moved to their positions 34, 39 thereby to impress the lower holding potential of source 36 across conductive strips 14a, 26a thereby to maintain the arc discharge in cell 22a, switch 42 remaining in this position 43-. When it is desired to extinguish the glow discharge in cell 22a, switch 42 is moved to position 44 thus reducing the potential applied iicrolss conductors 14a, 26a to a lower arc extinguishing eve It will be readily understood that in actual practice, the switching of the potentials applied to the conductive strips 14a, 26w may be accomplished by conventional static and/ or pulsed switching arrangements well known to those skilled in the art.

While cells 22 have been shown as being cylindrical and arranged in a regular geometric pattern with the conductive strips 14, 26 thus having a conventional crossgrid arrangement, it will be readily understood that the individual cells 22 may have other cross-sectional configurations and may be arranged in other patterns with the conductive strip electrodes being correspondingly rearranged.

Referring now to FIG. 3 in which like elements are indicated by like reference numerals, a modification is shown in which a flat plate 46 is employed formed of insulating material rather than the metal plate 11 of FIGS. 1 and 2 which thus permits elimination of the insulating coating 12. Here, the walls of the openings or cells 22 are tapered or flared outwardly toward the transparent plate member 25 to have a frusto-conical configuration so that their ends 23 exposed to the resistive layer 15 are smaller in diameter than their ends 27 which face the plate 25. In this embodiment, the phosphor layer 47 is deposited over the walls 48 of the cells 22 rather than on the transparent plate 25, the frusto-conical configuration of the cells thus permitting better viewing of the light emitted by the phosphor layer 47. This arrangement of the phosphor permits viewing of the light emitted by the surface of the phosphor which is excited by the ultra-violet radiation rather than the light attenuated by absorption in passing through the phosphor layer.

Referring now to FIG. 4 in which like elements are still indicated by like reference numerals, an embodiment is shown adapted for cathode ray switching. Here, plate 49 forms the faceplate of a cathode ray tube, shown in dashed lines at 50. Resistive layer 15, which acts as a current limiter, is deposited upon the outer surface of the faceplate 49 with the member 16 again positioned as shown. Faceplate 4-9 is provided with a plurality of discrete cathode wires or electrodes 52 extending therethrough and respectively into the openings or cells 22 as shown. Side 17 of member 16 and surface 20 defined by the recess 19 respectively have layers 53, 54 of conductive material coated thereon; layer 54 which surrounds end 27 of each cell 22 forms the anode whereas layer 54 which surrounds end 23 of each cell forms a holding electrode. A layer 55 of insulating material is preferably coated upon the resistive layer 15 within end 23 of each cell 22. Phosphor layer 28 is again deposited upon the inner side of transparent plate member 25, but in the alternative may be deposited upon the walls of the openings 22, as in the embodiment of FIG. 3.

Conductive layer 53 is coupled to switch 56 having first and second positions 57, 58 position 57 being coupled to source 59 of holding potential and position 58 being connected to source 60 of arc-extinguishing potential.

Con-ductive coating 54 is coupled'to 'the other side of sources 59, 60, as shown.

It will readily be seen that the individual cells 22 are triggered on by impingement of the electron beam 62 upon the respective electrode 52 which instantaneously raises the cell potential to the firing level. When the beam 62 moves on to another electrode 52 under the influence of conventional beam-deflection means (not shown), the glow discharge previously initiated in the respective cell 22 is maintained by virtue of the holding potential applied across conductive layers 53, 54 by switch 56 in its position 57. When it is desired to extinguish the display thus formed, switch 56 may be moved to position 58 thus applying the arc-extinguishing potential to the conductive layers 53, 54.

Referring now to FIG. 5 in which a modification of the embodiment of FIGS. 1 and 2 is shown, in order to minimize any cross-talk between adjacent cells 22 during operation, parallel channels 64 are provided in side 18 of member 16 interconnecting ends 27 of the openings 22 in lieu of the large-area recess 19 of FIGS. 1 and 2. Channels 22 may in turn communicate with a common header channel 65. Header channel 65 may thus serve as a reservoir for the gas, or may in turn be connected to a separate gas reservoir (not shown).

Referring now to PICS. 6 and 7 in which like elements are still indicated by like reference numerals, another embodiment of the invention is shown adapted for providing a multi-color display with either mixed or unmixed colors. Here, a flat cathode plate 11 is again provided preferably formed of thermal conductive material and having a thin layer 12 of insulating material deposited thereon. A plurality of enlongated, spaced, parallel conductive strips 14 are again formed on the surface of the insulating layer 12 and a layer 15 of suitable resistive material is deposited over the insulating layer 12 and the-conductive strips.

In this embodiment, member 16 has a plurality of clusters 66 of openings or cells 22 formed therethrough, each such cluster 66 including three such cells 22-1, 222, and 223. Member 16 is again arranged with its flat side 17 abutting the resistive layer 15 and with end 23 of the openings 22-1, 222 and 22-3 of each cluster 66 respectively in registry with conductive strips 14-1, 14-2, and 14-3. Channels 64-1, 64-2, and 64-3 are formed in side 18 of member 16 respectively communicating with ends 27 of the openings 22-1, 22-2, and 22-3, channels 64-1, 64-2, and 64-3 being connected by header or reservoir channel 65, as shown.

Another flat plate member 67 is provided which may be formed of suitable opaque insulating material and which has a plurality of openings 68 formed therein. A plurality of elongated spaced, parallel, conductive strips 26 having light transmitting characteristics are formed on the inner surface of plate member 67, conductive strips 26 extending transversely with respect to the conductive strips 14.

A plurality of small areas 69 of suitable phosphor material which emit visible light when stimulated by ultra-- violet light are deposited over the inner surface of plate member 67 and over the conductive strips 26. Plate member 67 with the conductive strips 26 and the phosphor areas 69 thereon is arranged abutting side 18 of member 16, conductive strips 26-1, 26-2, and 26-3 being respectively in registry with ends 27 of the openings 22-1, 222 and 22-3, and the phosphor areas 69 being respectively exposed to ends 27 of the openings. It will be seen that each of the openings 68 in the plate member 67 surrounds and defines a respective cluster 66, the openings 22-1, 222, and 22-3 which form a respective cluster 66 being in registry with a respective opening 68.

In this embodiment, each of the phosphor areas 69 for a respective cluster 66 emits visible light having a different color, such as the primary colors red, blue and v'ellow. Thus, the phosphor areas 69 respectively associated with openings 22-1, 22-2 and 22-3 of each cluster 66 may respectively be formed of phosphor materials emitting red, blue and yellow visible light.

In order to provide for mixing or blending of the colored light emitted by the phosphor areas 69 respectively associated with the cells 22-1, 222 and 22-3 forming each cluster 66, a suitable optical lens 70 is positioned in each of the openings 68 in the member 67.

It will now be seen that when a suitable potential, as above described, is applied to conductive strip 14-1 associated respectively with clusters 66a and 66b and to conductive strip 26-1 associated with cluster 66a, a discharge will be initiated in cell 22-1 of cluster 66a which will excite phosphor area 69 associated therewith to emit red light, which will be viewed through the lens 70. It will further be seen that if a suitable potential is initially applied to conductive strip 14-2 associated with clusters 66a and 66b and to conductive strip 26-2 associated with cluster 66a, a discharge will be initiated in cell 222 which will excite the phosphor area 69 associated therewith to emit blue light, the blue light thereby emitted and the red light emitted by the phosphor areas 69 associated with the cell 22-1of cluster 66a being mixed or blended by lens 70 to provide a resultant purple display.

It will now be seen that by the employment of a suitable switching arrangement, as is well known to those skilled in the art, any one of the three primary colors may be individually displayed in any one or more of the clusters 66a, or any mixture of the primary colors may be displayed in any one or more of the clusters 6612.

It will be readily understood that the embodiments of either FIG. 3 or FIG. 4 above may equally advantageously be modified to provide the multi-color display. It will also be readily understood that any desired combination of difierent colored phosphors may be employed in each of the clusters 66 and that each of the clusters 66 may comprise a greater number of cells 22 thus providing a greater range of individual colors and a greater range of color mixing.

While there have been described above the principles of this invention in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of the invention.

What is claimed is:

1. A character display panel comprising: means forming a plurality of cavities each having opposite ends respectively lying in spaced parallel planes; first electrically conductive means at one end of each of said cavities; fluorescent phosphor material exposed to each of said cavities; second electrically conductive means at the other end of each of said cavities; and means sealing said cavities; each of said cavities having glow discharge-inducing gas therein whereby selective application of electrical potential to said conductive means provides glow discharge in selected ones of said cavities and emission of light from the phosphor material respectively exposed thereto; at least a part of said sealing means having light-transmitting properties for transmitting the light emitted by said phosphor material for viewing; and current limiting resistance means connected to said first conductive means and exposed to said one end of each of said cavities for respectively ballasting the current of said glow discharge therein.

2. A character display panel comprising: a first member formed of insulating material and having flat opposite surfaces with a plurality of openings formed therethrough and respectively extending between said surfaces; a first flat plate member closely adjacent one of said surfaces; first electrically conductive means carried by said first plate member and positioned at one end of each of said openings; fluorescent phosphor material exposed to each of said openings; second electrically conductive means at the other end of each of said openings; a second flat plate member closely adjacent the other of said surfaces; and means sealing said plate members to said first member thereby sealing said openings therein; each of said openings having glow discharge-inducing gas therein whereby selective application of electrical potential to said conductive ineans provides a glow discharge in selected ones of said openings and emission of light from the phosphor material respectively exposed thereto; said second plate member having light-transmitting properties for transmitting the light emitted by said phosphor material for viewing; said first conductive means having a plurality of first elongated spaced parallel conductors carried by said first plate member, each of said openings having one end thereof in registry with one of said first conductors; said second conductive means having a plurality of second elongated spaced parallel conductors carried by said second plate member, each of said openings having its other end in registery with one of said second conductors; said first and second conductors extending transversely with respect to each other whereby application of said electrical potential to one of said first conductors and one of said second conductors causes a glow discharge in one only of said openings; said second conductors having light-transmitting properties; said openings being frustoconical with their said other ends being larger than their said one ends, and said phosphor material being deposited on the walls of said openings.

3. A character display panel comprising: a first member formed of insulating material and having flat opposite surfaces with a plurality of openings formed therethrough and respectively extending between said surfaces; a first flat plate member closely adjacent one of said surfaces; first electrically conductive means carried by said first plate member and positioned at one end of each of said openings; fluorescent phosphor material exposed to each of said openings; second electrically conductive means at the other end of each of said openings; a second flat plate member closely adjacent the other of said surfaces; and means sealing said plate member to said first member thereby sealing said openings therein; each of said openings having glow discharge-inducing gas therein whereby selective application of electrical potential to saidconductive means provides a glow discharge in selected ones of said openings and emission of light from the phosphor material respectively exposed thereto; said second plate member having light-transmitting properties for transmitting the light emitted by said phosphor material for viewing; said first conductive means having a plurality of first elongated spaced parallel conductors carried by said first plate member, each of said openings having one end thereof in registry with one of said first conductors; said second conductive means having a plurality of second elongated spaced parallel conductors carried by said second plate member, each of said openings having its other end in registry with one of said second conductors; said first and second conductors extending transversely with respect to each other whereby application of said electrical potential to one of said first conductors and one of said second conductors causes a glow discharge in one only of said openings; said second conductors having light-transmitting properties; and a layer of resistance material deposited on said first plate member and said first conductors, said resistance material being exposed to said one end of said openings for ballasting the current of said glow discharge therein.

4. The panel of claim 3 wherein areas of secondary electron emissive material are deposited on said layer of resistance material respectively in said one each of said openings.

References Cited UNITED STATES PATENTS 2,757,302 7/1956 Hughes 313-92 2,760,119 8/1956 Toulon 313- 2,895,079 7/1959 Willard 315-169 2,933,648 4/1960 Bentley 315-169 2,991,394 7/1961 Archer et al. 3l3-108 3,042,823 7/1962 Willard 315169 3,157,824 11/1964 Jones 315-169 3,206,638 9/1965 Moore 315-l69 3,264,074 8/1966 Jones 315169 JAMES W. LAWRENCE, Primary Examiner. R. JUDD, Assistant Examiner. 

1. A CHARACTER DISPLAY PANEL COMPRISING: MEANS FORMING A PLURALITY OF CAVITIES EACH HAVING OPPOSITE ENDS RESPECTIVELY LYING IN SPACED PARALLEL PLANES; FIRST ELECTRICALLY CONDUCTIVE MEANS AT ONE END OF EACH OF SAID CAVITIES; FLUORESCENT PHOSPHOR MATERIAL EXPOSED TO EACH OF SAID CAVITIES; SECOND ELECTRICALLY CONDUCTIVE MEANS AT THE OTHER END OF EACH OF SAID CAVITIES; AND MEANS SEALING SAID CAVITIES; EACH OF SAID CAVITIES HAVING GLOW DISCHARGE-INDUCING GAS THEREIN WHEREBY SELECTIVE APPLICATION OF ELECTRICAL POTENTIAL TO SAID CONDUCTIVE MEANS PROVIDES GLOW DISCHARGE IN SELECTED ONES OF SAID CAVITIES AND EMISSION OF LIGHT FROM THE PHOSPHOR MATERIAL RESPECTIVELY EXPOSED THERETO; AT LEAST A PART OF SAID SEALING MEANS HAVING LIGHT-TRANSMITTING PROPERTIES FOR TRANSMITTING THE LIGHT EMITTED BY SAID PHOSPHOR MATERIAL FOR VIEWING; AND CURRENT LIMITING RESISTANCE MEANS CONNECTED TO SAID FIRST CONDUCTIVE MEANS AND EXPOSED TO SAID ONE END OF EACH OF SAID CAVITIES FOR RESPECTIVELY BALLASTING THE CURRENT OF SAID GLOW DISCHARGE THEREIN. 